1. Field of the Invention
This invention relates to a motor-driven marine propeller for propelling a marine vessel or the like. More specifically, this invention relates to a marine propeller having a can for the passage therethrough of exhaust generated by the motor.
2. Information Disclosure Statement
Can-type propellers have been used extensively for propelling high speed motor boats, particularly boats used in bass fishing tournaments. Can-type propellers include a central hub driven by an outboard motor. A can disposed coaxially with the central hub is connected to the hub by radially extending webs and the exhaust generated by the motor is directed through the annular port defined by the hub and the can. A plurality of blades, usually three, extend substantially radially from the can such that as the hub is driven by the motor, rotational movement is transmitted to the can and attached blades by means of the radially extending webs.
While some cans are essentially cylindrical, the aft end of the can on some can propellers is flared ouwardly on the outer can surface or the inner can surface or both such that as the propeller rotates for providing forward motion to the boat there exists a tendency to decrease pressure in the water behind the aft end of the can thereby assisting the scavenging of gaseous exhaust from the fore to the aft end of the can.
However, with the aforementioned prior art propellers, as the blades rotate in the water, eddies are generated in the vicinity of the trailing surfaces of the blades. Consequently, proposals have been developed in which a portion of the exhaust is directed through holes in the fore end of the can such that this portion of the exhaust will flow along the trailing surface of the blades and assist the smooth flow of water from the fore to the aft end of the can.
An example of the aforementioned proposal in which a portion of the exhaust is bypassed is disclosed in U.S. Pat. No. 3,788,267 to Strong.
U.S. Pat. No. 3,788,267 teaches that cavitation most often occurs in high speed propellers and discusses the effects of polishing the blades. However, this disclosure emphasizes that due to mass production adequate polishing is not always possible. Part of the exhaust is permitted to pass through axially spaced holes thereby enabling the inhibition of cavitation bubbles on the surfaces of the blades.
Another problem encountered by high speed motor boats is the entanglement of water weeds around the propeller.
U.S. Pat. No. 4,080,099 to Snyder teaches a plurality of weedcutting fingers radially offset from the propeller shaft for cutting entangled weeds.
Although the prior art propellers have, to a degree, avoided cavitation bubbles, and cutting devices have been proposed for cutting entangled weeds and fishline and the like, the present invention not only combines these characteristics but also provides an improved configuration which enhances performance and efficiently cuts through entangling weeds. Therefore, it is a primary object of this invention to provide a marine propeller that overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which significantly contributes to the overall performance of a marine propeller or the like.
Another object of the present invention is the provision of a marine propeller having a plurality of notches defined by the fore end of the can member, each of the notches being disposed adjacent to a trailing surface of an adjacent blade thereby enhancing relief of exhaust gas and assisting the smooth flow of water from the fore to the aft end of the can member.
Another object of the present invention is the provision of a marine propeller in which each of the notches is triangular in configuration with the triangular configuration being right angled to include a first edge which extends substantially parallel to the axis of rotation of the propeller for cutting through filamentary material entangled around the propeller.
Another object of an alternate embodiment the present invention is the provision of a marine propeller in which each of the notches is in the form of a slot substantially parallel to the root portion of the adjacent blade for cutting through filamentary material entangled around the propeller.
Another object of the present invention is the provision of a marine propeller in which the apex of each of the plurality of notches enables part of the exhaust to pass along the trailing surface of an adjacent blade rearwardly across the outer surface of the can member towards the aft end of the can member and towards the leading surface of an approaching blade during rotation of the propeller thereby reducing the generation of eddies and assisting in the displacement of fluid in front of each leading blade surface of the propeller.
Another object of the present invention is the provision of a marine propeller in which the fore end of the can member defines an annular lip which is of reduced thickness relative to the thickness of the remainder of the can member such that the annular lip cooperates with an exhaust conduit of the motor such that a portion of the exhaust is conducted past the lip and through the annular port defined by the hub and the can member.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Particularly, with regard to the use of the invention disclosed herein, it should not be construed as being limited to propellers for marine application, but should include any propeller rotating within a fluid. More particularly, the term "marine propeller" should not be taken to limiting the use of such propeller for propelling boats through the sea or ocean but should include propellers for use in fresh water lakes, rivers and the like.